Effects of some plant growth promoting rhizobacteria treated twice on flower thining, fruit set and fruit properties on apple

The objective of this study was to determine the effects of inoculation bacteria (Agrobacterium rubi A-18, Bacillus subtilis OSU-142, Burkholderia gladioli OSU-7 and Pseudomonas putida BA-8) treated twice on flower thinning, set and fruit properties of apple cultivars, Starking Delicious, Granny Smith, Starkrimson Delicious and Starkspur. Golden Delicious cultivars grafted on MM 106 were used as plant materials. The suspensions prepared with bacteria strains were applied to crown of trees by spraying at the periods of first blooming and full blooming. Fruit set rate showed significant differences among the cultivars. Starkspur Golden Delicious cv. had the highest fruit set with a rate of 12% while Granny Smith cv. had the lowest fruit set with a rate of 4%. Bacterial treatments decreased fruit set by 12% (OSU-142) and 33% (A-18 and BA- 8). The bacterial treatments had no significant effect on fruit size, width and height of fruit; but it decreased specific gravity of fruit, stalk thickness, stalk length and stalk hole deepness. The bacterial treatments generally reduced the rate of total soluble solid, total sugar, reduced sugar, ascorbic acid contents, titrable acidity and pH rate.